[Onkel_Tom]

Also if you are using an older version of php the $_SERVER command could be a problem.
To verify it you can open the file /includes/functions_statistik.php and at the beginning near line 26 you'll find the line:

$agent = $_SERVER['HTTP_USER_AGENT'];

You can change that to the line before which should read:

$agent = getenv("HTTP_USER_AGENT");

But if your Browsers are still identified with the $_SERVER Command also search engines should be identified by this command !